Brazing is a technique used to physically join multiple metallic structures together. In conventional brazing techniques, metallic structures and a filler metal are heated, causing the filler metal to melt and flow into at least one joint between the metallic structures. The filler metal then cools and hardens to create a metallurgical bond between the metallic structures, physically attaching the structures. The filler metal has a lower melting point than the metallic structures, allowing the filler metal to be heated without adversely affecting the metallic structures.
In some situations, it may be necessary or desirable to limit the flow of the filler metal between the metallic structures being joined. For example, there may be a need to prevent the filler metal from inadvertently brazing surfaces not intended to be connected. There may also be a need to prevent the filler metal from clogging one or more tubes, orifices, or other portions of the structures.
One conventional approach to limiting the flow of filler metal during brazing is to apply a braze stop-off material to one or more of the metallic structures. A braze stop-off material typically represents an oxide material or other material that is applied to part of one or more of the metallic structures. The braze stop-off material reduces or prevents the migration of the filler metal over that part of the metallic structures, thereby limiting where the metallic structures are brazed together by the filler metal. Braze stop-off materials are typically applied to metallic structures by hand, such as by painting or spraying.